Arc-lamp electrode.



. N TE sTATEs" PATENTOFFIGE.

' HENRYSTAFFORD HATFIELD AND FRANK. MICHAEL LEWIS, F BRIGHTON, ENGLAND.

' ARC-LAMP ELECTRODE.

Specification 61 Letters Patent. i

am n w. 24, 1908.

To all whom it may; concern:

Be it known that we, HENRY STAFFORD HATFIELD, residing at 18 Palmeira Square,

Hove, Brighton, in the county of Sussex,England, electrochemist, and FRANK MICHAEL Liawrs, residing at 11 Buckingham road, Brighton, in the county of Sussex, England, electrical engineer, have invented new and useful Improvements in- Arc-Lamp Electrodes, of which the following is a specification. 1 Y Our invention is not concerned with such flfiame arc lamps as use a non-carbon elect-rode, such as oxid of iron with oxidof titanium added. On the other hand our infound possible to burn such carbons in an inclosed or. air-tight globe for the reason that the large amount of salt vapor emitted from the arc condenses on the inolosing globe and prevents the proper emission o and for the further reason that the arc is so unsteady asto fail to meet present-day requirements. But the importance of burning carbons inclosed, that is to say of using an arc lamp of the inclosed variety, is well recognized since it reatly diminishes the consumption of the e ectrodes. f

We have been enabled to 'produce'anarc lamp of the inclosed variety using a carbon to which a-metallic fluorid has been added electrode, which consists of twenty-five per cent. of calciumiiuorid and seventy-five per,

as a flaming material,-and this without interfering with the steadiness of the light,

by adding to the carbon and the metallic fluorid silicon in an incompletely oxidized form. Thus for exam lo we have found that adding, to the-Wel known are lamp cent. of pure carbon, silicon in theform of carborundum and to the extent of five, to ten per cent. greatly improves the me-" chanical strength ofthe electrode and "also thev steadiness of the light given by it, when the arc is burned without access of air.

We use the term incompletely oxidized light silicon to denote the 'forms of silicon in which its full valencfor or power of taking up. oxygen has not een substantially satisfied as is the case with silica (SiO, or the silicates. Thus under the term incompletely carborundum. So, too, we include compounds in which thesilicon is combined with oxygen but not to the full extent required to form silica -(SiO,). Such a compound is that known as siloxicon- SiOC. These bodies roduce the desired good result and we be-' ieve that this-is due to the fact that they supply siliconvapor to the arc. Silica and silicates on the other hand do not produce the required results and we'believe'that this is due to the fact that these compounds of silicon and'oxygen' are not decomposed at the temperature of the-arc.- We therefore make 'no claim to the-use of silicaor silicates. We have obtained good results by of calcium fluorid. and carborundum requires such a high temperature to fuse'properly that it is apt ,to accumulate on the electrodes. To obviate this we find it advantageous to add a flux such for example as the fluoride of barium-magnesium and strontium, cryolite, burnt clay and the like. a We claim,

1. A11 inclosed arc. lamp, having .its inclosed and light-giving electrode containing carbon, a metallic'fluorid, and silicon in an incompletely oxidized condition to improve the steadiness of the described.

2. An inclosed arc lamp having its inclosed and light-giving electrode containing carbon,- a metallic fluorid and carborundum to improve the steadiness of the light, substantially as described. 3.-An inclosed arc lamp having its inlight, substantially as closed and light-giving electrode composed Tn Witness whereof we have signed our 10 r of some eight parts of calcium fluorid, five names to this specification in the presence parts of carborundum, and carbon, substanof two subscribing Witnesses. tially as described. I l 5 4.-An inclosed arc lamp having its in- HENRY STAFFORD HATFIELD.

closed and light- 'ving electrode containing FRANK MICHAEL LEWIS. carbon, calcium (florid and carborundum to Witnesses: 7 im love the steadiness of the light, substan- F. L. RAND, tia' ly as described. R. J. WILLIAMS. 

